Dave Johnson designed the following detectors , he said his favourite is the Tesoro uMax
Fisher in California: 1260, 1220, 1210, 1235, 1225, 1212, 1265, 1266, CZ6, CZ5, CZ20, original Gold Bug, Gold Bug II, Gemini, and industrial instruments including TW6, FX3, XLT-16, PF-18, and circuitry of the TW-770.
Tesoro: Diablo uMAX , Lobo SuperTraq.
White's: GMT, MXT, analog circuitry of DFX, Beach Hunter and PCL-600 line tracer.
Troy: X-5 and X-3.
FTP Bounty Hunter: major revisions to existing platforms most of which originated with George Payne. The BH Junior, Platinum, Gold and security wand (sold under various trademarks) were new designs.
FTP Teknetics: T2, Alpha, Delta, Gamma, Omega, G2.
FTP Fisher: F2, F4, F5, F75, F70, new Gold Bug, circuitry of the TW-82 industrial line tracer.